 /*******************************************************************************
  * Copyright (c) 2002, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal.cheatsheets;

 import java.util.ArrayList ;
 import java.util.Iterator ;
 import java.util.List ;

 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.ListenerList;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.ui.IMemento;
 import org.eclipse.ui.IPropertyListener;
 import org.eclipse.ui.internal.cheatsheets.registry.CheatSheetElement;
 import org.eclipse.ui.internal.cheatsheets.registry.CheatSheetRegistryReader;

 /**
  * This is used to store the most recently used (MRU) list
  * of cheatsheet for the entire workbench.
  */
 public class CheatSheetHistory {

     private static final int DEFAULT_DEPTH = 5;
     
     private ArrayList history;
     private CheatSheetRegistryReader reg;
     private ListenerList listeners = new ListenerList();

     public CheatSheetHistory(CheatSheetRegistryReader reg) {
         this.history = new ArrayList (DEFAULT_DEPTH);
         this.reg = reg;
     }

     public void addListener(IPropertyListener l) {
         listeners.add(l);
     }
     
     public void removeListener(IPropertyListener l) {
         listeners.remove(l);
     }
     
     private void fireChange() {
         Object [] array = listeners.getListeners();
         for (int i = 0; i < array.length; i++) {
             IPropertyListener element = (IPropertyListener)array[i];
             element.propertyChanged(this, 0);
         }
     }
     
     public IStatus restoreState(IMemento memento) {
         IMemento [] children = memento.getChildren("element"); //$NON-NLS-1$
 for (int i = 0; i < children.length && i < DEFAULT_DEPTH; i++) {
             CheatSheetElement element =
                 reg.findCheatSheet(children[i].getID());
             if (element != null)
                 history.add(element);
         }
         return new Status(IStatus.OK,ICheatSheetResource.CHEAT_SHEET_PLUGIN_ID,0,ICheatSheetResource.EMPTY_STRING,null);
     }
     
     public IStatus saveState(IMemento memento) {
         Iterator iter = history.iterator();
         while (iter.hasNext()) {
             CheatSheetElement element = (CheatSheetElement)iter.next();
             if(element != null) {
                 memento.createChild("element", element.getID()); //$NON-NLS-1$
 }
         }
         return new Status(IStatus.OK,ICheatSheetResource.CHEAT_SHEET_PLUGIN_ID,0,ICheatSheetResource.EMPTY_STRING,null);
     }

     public void add(String id) {
         CheatSheetElement element = reg.findCheatSheet(id);
         if (element != null)
             add(element);
     }
     
     public void add(CheatSheetElement element) {
         // Avoid duplicates
 if (history.contains(element))
             return;

         // If the shortcut list will be too long, remove oldest ones
 int size = history.size();
         int preferredSize = DEFAULT_DEPTH;
         while (size >= preferredSize) {
             size--;
             history.remove(size);
         }
         
         // Insert at top as most recent
 history.add(0, element);
         fireChange();
     }
     
     public void refreshFromRegistry() {
         boolean change = false;
         
         Iterator iter = history.iterator();
         while (iter.hasNext()) {
             CheatSheetElement element = (CheatSheetElement)iter.next();
             if (reg.findCheatSheet(element.getID()) == null) {
                 iter.remove();
                 change = true;
             }
         }
         
         if (change)
             fireChange();
     }

     /**
      * Copy the requested number of items from the history into
      * the destination list at the given index.
      *
      * @param dest destination list to contain the items
      * @param destStart index in destination list to start copying items at
      * @param count number of items to copy from history
      * @return the number of items actually copied
      */
     public int copyItems(List dest, int destStart, int count) {
         int itemCount = count;
         if (itemCount > history.size())
             itemCount = history.size();
             
         for (int i = 0; i < itemCount; i++)
             dest.add(destStart + i, history.get(i));
             
         return itemCount;
     }
 }


